Method of lapping valve plugs



Jan. 6, 1942,

e. F. SCHERER METHOD 0F -LAPPING VALVE PLUGS Filed NOV. 12, 1938 7 Z7ZIP *715 g l QQJ INVENTOR- Geoye/Eibererr which a changes.

"ast a. 1942 UNITE STATE! Mnrnon or LAPPING vulva mes George Scherer,San Francisco, assigm" J or to Merco Nordstrom Valve Company,Pittsburgh, Pa., a corporation of Delaware r a Application November 12,weas l-a1 No. 239,995 (Cl; 51-281) 13 Claims.

The present invention relates to plug valves intended for hightemperature service. a

It has heretofore been observedthat when plug valves, whether lubricatedor not, which have been'carefully lapped and adjustedtobe seater sneueextending missiles tin upright ed against the pressure carriedby theline at ordinary temperatures, are. subjected to services carrying fluidat elevated temperatures, the

valves frequently become stuck or develop leaks,

or both. According to the present invention, 1 fit the valvemember of avalve intoits' seat at a temperature'. above normal or room temperature,

preferably substantially at the temperature for the valve, or formaintaining-the valve atf'ali elevated temperature duringtheflttingopera- ,tion, and the fitting operation may be carried out inany suitable way. For example, in applying the invention to a plugvalve, the valve may be submerged in a bath of high boilin mineral oil,molten metal, or a sand bath or other heat post. 9, suitably supported.A; gas burner It or other suitable source of heat is provided beneath Vthe tank 6' for heating'the'liquid therein. The

liquid inthe tank maybe any suitable hydrocar bon oil boiling above thetemperature at'which .the lapping opera'tionis tobe-performed, or mayconsist of diphenyl, a metal having allow melting point, or a bath ofsand. The plug H, of the i5 carried by the spindle l6 so that the plugmay J freely center itself with respectto the valvefseat l'linthecasing;I Spindle lids rotatably supported in, the sleeve is mounted in theouterend of a bracket supported by the upright 9, and the rear, side ofsleeveiS is provided with arack 2i meshing with a gear mounted on ashaft 24 journalled in the bracket 20. If desired, one endoff shaft 24may be square to receive the inner end ota handle 25 carrying a weight26. The upper end of spindle I'B 'is'joumalled in the'projectingfpart 21of theiupright 9 and has abevel gear 28 rest- 7 ing on the extension,the Bear .28 being splined transfer medium heated by agas burner orother suitable-source of heat, and, lapped at tempera-- tures of about400 Fahrenheit to. 1000" Fahrenor. at anyother temperature above room ornormal temperature at which thef'valvesare to be operated in service.The lapping compound on the upper end of the spindle l6 so that thespindle may be moved axially therethrough while the gear'is rotating,Gear 28 is driven by bevel gear on one end of-a horizontal shaft 31.journalledin the brackets 32 and 33 and carrying a step pulley 34 whichmay bedrive'n from any may consist of finely divided *Carborundum orother suitable abrasive suspended in a suitable carrier such as anon-volatile or onlyslightly volatile mineral 011. After lapping theplug, the

valve is removed fromthebath,- cleaned, assembled and tested at thetemperature of the lappingoperation, of lapping the valve, the fittingmay be accomplished by anyother .method of grinding or by machining atelevated temperatures. n 1 a p v The invention will be described indetail in connection with the aoooncipany-ing drawing, in

Figure 1 shows a preferred apparat for carrying out the method, andvFigures 2 and 3 show diagramm'atically my theory of the distortion dueto temperature Referring to Figure 1, a valve ca g 4, shown inlongitudinal section, is loosely hel' in a cradle 5 supported on thebottom of a B which may be filled with oil 1 above the levelgot theconvenient source of. power. 7

During operation, while the plug rotating,

it is periodically lifted and returnedto its seat.-

This is accomplished by a mechanism compris- 85 ing a cam 36 secured tothe shaft 24 co-operating with a cam 31 secured on one end of shaft 39which is ioumalled in bracket 20. Shaft 39 car- Y ries a gear 4| meshingwith a gear 42 secured to.

a shaft 43 journalled in an arm 44 of extension .40 20 and a-boss 46 atthe,top .A gear at the top of shaft 43 meshes with a gear 48 carried bya shaft 3|. Preferably, the gearing ratio is such that plug'll does notmake a complete revolution in the valve seat when it"is lifted by theengagement of cams 36 and 31, although if desired, the

plug may make slightly more than one revolu-" tion before 'it is lifted.Also, it will be understood that instead of rotating theplug it may beoscillated back and forth and periodically lifted,

50 or the lapping operation may be carried out with any other motionknown in the art.

The abrasive compound used for the lapping operation preferably consistsof 'a mixture of a high boiling mineral oil and a line grade of valve.The tank 8 may be supported ma ame fCarborundum abrasive powder, and ifdesired,

valve having a port I2 is held loosely by a chuck the lapping compoundmaybe thickened by the addition of asphalt or other suitable thickeningagents. The actual proportions and type of material used for the lappingoperation may be varied in known manner in accordance with the nature ofthe metal of which the valve is made, and the temperature at which. thelapping operation is carried out.

A mineral oil bath may be used for carrying out the lapping operation upto about 600 Fahrenheit, and for higher temperatures the sand bathmethodmay be employed, as most oils are volatile abovethis temperature.It will also valve port and passage are ground 01!, thus producing aplug having a circular form at the elevated temperature at which lappingoccurs, which has aperfect lit with the seat. It is, of course,apparent'that when a valve is so lapped and fitted at a high temperatureit will assume a slightly oval shape in cross section at lower tembeunderstood that, if desired, the bath may be made up of molten lead or,other solid material having a suitable high boiling point so that itwill not be volatilized at the temperature at which the lappingoperation is carried out. The lapping operation may be carried out atany de-.-

sired temperature up to about 1000 Fahrenheit.

or higher. 7

I believe that the difficulties heretofore experienced in attempting tooperate cold lapped valves at elevated temperatures is due to theunequal expansion of the metal, which results from the fact that thevarious sections of metal in the valve are not of equal thickness. Thus,referring to Figure 2, if a plug ll having a port I! therethrough isheated, the chord 5| forming the walls of the port-will expand greaterthan the wall"along the transverse diameter, indicated by thedot anddash line-I2, and the edges ofthe port will form projecting lips. Theselips may-project about ten thousandths of an inch or more, depending onthe temperature, properties of the metal, and relative sizes oi: thevarious sections. In other words, the plug will assume agenerallyelliptical shape between the ends of the port, as indicatedbythe dot and dash line 53. At the same time the seat II will expandunequally,'the lips 54 adjacent the: passageway expanding less than therest of the seat and as a .iWhile I have illustrated peratures. However,in lubricated valves, the

slight oval shape appears to have no disadvantage, as the lubricant hassufllclent viscosity at low temperatures to provide an adequate seal forthe valve. In such a valve, although the viscosity of the lubricant'isreduced at higher temperatures, the closer fit of the plug and seatcompensates for the decrease in efliciency of the lubricant film andprovides a satisfactory seal.

The temperature at which difliculties in operation will be experiencedwith cold lapped valves will depend on the nature of the metals in thevalve, and on other factors. In general, ordinary carbon steel or alloysteels intended for operation at temperatures at or above 400 Fahrenheitshould be hotilapped according to the present invention.

At high temperatures a close fit of the plug to its seat isquiteessential because at such temperatures the lubricants-employed losetheirviscosity and sealing properties, whereas in a valve which has a loosefit at low temperatures it is not ditlicult to provide lubricant at suchtemperatures having the proper viscosity to seal the valve and'preventleakage.

to a plug'valve, it will be understood that the inresult the 1ips53 ofthe plug port wi1l-abut vention may be applied to. any other type ofvalve. without departing from the spirit. or scope thereof;

What I claim as my invention and desire to secure by Letters Patent is:

1. The method of fitting a valve plug into its seat whichc'ompriseslapping the plug in its seat in the presence of an abrasive lappingcompound at a temperature above normal tionof extraneous heat.

' 2. The method of fitting a valveplug into its seat which compriseslapping the plug in' its seat in the presence of an abrasive lappingcompound by the. applicaat a temperature of about 400 Fahrenheit orhigher. V

3.'In the manufacture of a plug valve, the method which comprisescutting the plugmemher and its seat, to a' substantially circular crosssection form at a temperature above normal obtained by the applicationofextraneous heat.

. GEORGE my method applied

